In motor vehicle service stations devices are provided for measuring the slack in the vehicle articulated joints. These devices comprise a lower plate and an upper plate movable horizontally relative to the lower plate in the two perpendicular directions. These devices are generally installed in pairs on a vehicle lift, the lower plate being fixed to the corresponding runway and the upper plate supporting a wheel of the vehicle which is to be checked and which has previously been driven onto the lift. To determine the presence of any slack in the articulated joints of the steering system and to measure its extent, the upper plate is made to move relative to the fixed lower plate while observing the behavior of the vehicle during these movements, viewing from below with the aid of an electric lamp.
A drawback of this known device is that it has a rather large height (about 7 cm), and as it is generally installed permanently on the vehicle lift that can in practice be used only for this purpose.
Circular ball plates are also known for measuring the suspension geometry and the wheel steering angles. They are also generally mounted on the vehicle lift runways in suitable recesses provided within them, so restricting their use to this one purpose because of their particular configuration and the nature of the functions performed.
Hence those vehicle service stations equipped both for determining slack and for measuring steering angles must necessarily be provided with two vehicle lifts or in any event two separate stations, one equipped with the accessories of one type and the other equipped with the accessories of the other type, with obvious cost and space considerations.
Alternatively, the accessories for the two different measurements could be mounted interchangeably on one and the same vehicle lift, but this would require a series of operations for installing the appropriate accessories before effecting a given type of measurement and their removal after making this measurement.